Synchronizing-signal generator



H. M. LEWBS SYNCHRQNIZING-SIGNAL GENERATOR 2 Sheets-Shee t 1 Filed July27, 1940 FIG. I.

INVENTOR HAROLD m. LEWIS AORNEY Patented Dec. 9, 1941 UNITED 4 STATESPATENT OFFICE ;f

smcmaomm s rz sn air-Neuron I ware . Harold M. Lewis, 'Great'Neck, N.Y.,assignor to I Baseltine Corporation, a corporation of Dela- ApplicationJuly 2'1, 1940, Serial No. 347,817 13 Claims; (01. ire-7.2)

This invention relates to synchronizing-signal generators for televisiontransmitters and, while the generator of the invention is of generalutility, it is particularly useful in a portable television transmitterbecause of the relatively small amount of apparatus comprised in thegenerator.

It is conventional to develop at a television transmitter a compositesynchronizing signal includingiine-synchronizing components andfieldsynchronizing components for transmission with the video-signalcomponents on a common carrier wave. Such a composite signal hasconveniently been developed by the artifice of generating each of therequired synchronizing-signal components in vacuum-tube circuits andcombining the generatedcomponents in other vacuumtube circuits todevelop a composite synchronizing signal. Very, complicated circuitarrangements have been provided for the purpose. Thus, it has beencustomary to provide a "timer chain" which is synchronized from thealternating current source for the transmitter and which developsoscillations of suitable frequencies for developing and keying therequired pulses into the composite synchronizing signal. Also, thecomposite synchronizing signals generally utilized are suitable foreffecting multiple-interlaced scanning, and such systems requiresynchronizing-signal components during one field period which aredliferent from those during a succeeding field period. Thus, the featureof multiple interlace in a television system also adds materially to thecomplexity of the apparatus required for generating the required type ofcomposite synchronizing signal. Furthermore, the composite synchronizingsignals conventionally utilized for multiple-interlaced scanning systemscomprise line-doubling components in thesignal.

preceding and succeeding the field-synchronizing components of thesignal. These linedoubling pulses have been provided in the same mannerdescribed above, rendering the apparatus required still morecomplicated.'-

Furthermore, the signal components of a com-- posite synchronizingsignal, developed'in the manner described above, may require considerone or more of the above-mentioned disadvantages of prior artgenerators.

In accordance with the invention, a nizing-signal generator for atelevision transmitter, adapted to generate a synchronizing signal foruse in a multiple-interlaced scanning system in which synchronizingcomponents thereof during one field periodare different from thoseduring a succeeding field period. comprises a device .including aplurality of radially-displaced circumferential patterns havingpredetermined angular portions thereof corresponding to predeter-j minedportions of the signal to be generated.

Means are provided for continuously scanning I the patterns insuccessive substantially circumferential paths having predeterminedangular portions radially displaced on the device and corresponding tothe dissimilarity of the field periods oi the desired synchronizingBisnal to develop an electrical effect corresponding to the patternscanned.

In accordance with a preferred embodiment of the invention, theabove-mentioned portions of the circumferential patterns correspond.rapestively; to the portions of the signal to be generated including theline-synchronizing components; which line-synchronizing components ofone .field period are substantially differently spaced with reference tothe field-synchronizing components than are the line-synchronizing 85portion corresponding to the field-synchronizing components to begenerated and the other comprises a portion corresponding totheline-synchronizing components to be generated. Inaccordance with apreferred modification of this 4 last-mentioned preferred embodiment ofthe invention, the pattern corresponding to the fieldsynchronizingcomponents comprises substantially all of one of theabove-ment'ionedcircumable shaping in order to procure" satisfactory" operation. It is,therefore, also desirable to provide a synchronizing-signal generator inwhich the individual components are of a uniform and preciselydetermined wave form.

It is an object of the invention, therefore, to

provide improved television synchronizingsignal generator which iseffective to eliminate the appended claim 7 ferential patterns andanother of the circumferential patterns, corresponding to thelinesynchronizing components to be generated, is I scanned a pluralityof times for each s'cansion of the pattern corresponding to thefield-scanning period.

For a better understanding of the present invention, together with otherand further objects thereof, reference is had to the followingdescription taken in connection with the accompanying drawings. and itsscope, will be pointed out in synchroi Fig. 1 of the drawings is acircuit diagram, partly schematic, of a complete televisionsignalgenerating and -transmitting station including asynchronizing-signal generator in accordance with the present invention;Fig. 2 is a detail illustrationpf a portion of the synchronizing-signalgenerator of Fig. 1; Figs. 3a and 3b are graphs .of wave forms developedby a modification of the generator of Fig. 1 while Fig. 3c is a detailillus tration of a modification of the generator of Fig. 1 forgenerating the wave forms of Figs. 3a

and 3b; Fig. 54 is a schematic diagram of a synchronizing-signalgenerator in accordance with the present invention which comprises ascanning disc; Fig. 5 is a circuit diagram of a further modification of.the synchronizing-signal generator of Fig. 1; while Fig. 6 illustratesin detail a portion of the modified synchronizing-signal generator ofFig. 5.

Referring now more particularly to the drawings, in Fig. 1 there isshown a complete television signal transmitter in accordance with theinvention. This transmitter comprises a conventional signal-generatingand-transmitting circuit adapted to be synchronized by, and to transmita composite synchronizing signal developed by. a synchronizing-signalgenerator constructed in accordance with the present invention; that is,a modulated-carrier signal is developed for radiation by an antennacircuit l2, l3 which comprises, as modulation components thereon, thevideo signals to be transmitted and the composite synchronizing signalgenerated b the synchroniz ng-signal generator |l.

The synchronizing-signal generator II, which is adapted to generate asynchronizing signal for use in a multiple-interlace scanning system inwhich synchronizing components thereof during one field period aredifferent from those-during a successive field period, includes acathode-ray tube |5 having therein an electron gun comprising a cathodel4, a control electrode I6, first and second accelerating anodes I1 andHi, a target electrode l9, and a collector electrode 20, together withsuitable horizontal and vertical defleeting electrodes 2|, 22 and 23,24, respectively. Suitable unidirectional operating potentials areprovided for cathode-ray tube |5 in a conventional manner. Targetelectrode |9 includes a surface having thereon a plurality of, orspeferential pattern including portionsF, F; corresponding to thefield-synchronizing components of the composite signal to be generated,a circumferential pattern including carbon deposits L corresponding tothe line-synchronizing components of one field period of thesynchronizing signal to be generated,and a radially displaced Icircumferential pattern including carbon deposits L corresponding to theline-synchronizing combe considered to comprise field-synchronizingcomponents and line-synchronizing components of one field period whichare differently spaced with reference to the field-synchronizingcomponents than the line-synchronizing components of the succeedingfield period.

In order to develop a composite synchronizing signal by means of thecathode-ray tube synchronizing-signal generator ofFig. 1, the patternsof target electrode 9 are continuously scanned in successivesubstantially circumferential paths, having predetermined angularportions radially-displaced on the target electrode l9 andcorresponding-to the dissimilarity between successive field'periods ofthe desired synchroniz-.

ing signal, to develop an'electrical signal corresponding to the patternscanned. Scanning circuits are provided for the cathode-ray tube l5 sothat the .cathode ray of the tube scans the patterns on target electrodeI9 in substantially circular paths. In order to provide the requiredscanningpotentials for cathode-ray tube I5, the

primary winding of a transformer 28 is connected to a suitablesinusoidal alternating current source, for example, the 60-cycle supplycircuit. Secondary windings 29 and 30 of transformer 28 are coupled totwo suitable phase-splitting circuits in order to developphase-displaced voltages. One of the phase-splitting circuits includesseries-connected condenser 3| and resistor 32 coupled across windings 29and 30 in series through resistors 33 and 34, while the other of thephase-splitting circuits includes a series-connected condenser 35 andresistor 36 connected across windings 29 and 30 in series throughresistors 3'! and 38. The coupling resistors 33, 34 and 31, 38 aresufficiently large so that the current in each phase-splitting circuitis substantially in phase with the secondary voltage of transformer 28.Therefore, the voltage across condenser 3| is in quadrature with thatacross resistor 32 and the voltage across condenser 35 ponents of thesucceeding field period of the composite signal to'be generated. Thatis, the composite synchronizing signal to be generated can 75 is inquadrature with that across resistor 35. The

voltages across condensers 3| and 35 are, however, of opposite polarityand are applied, respectively, to the control electrodes of tubes 39 and40 to develop a balanced sinusoidal output voltage across load resistors4| and 42 provided for tubes 39 and 40, respectively. This outputvoltage is applied to the horizontal deflecting plates 2| and 22 by wayof coupling condensers 43 and 44. A resistor 45 is coupled betweendefleeting electrode 22 and a tap 46 of a potential divider 41 toprovide horizontal centering of the cathode-ray beam of tube l5 prior todeflection.

The voltages across resistors '32 and 36 are also of opposite polarityandare applied, respectively,

to the input electrodes of tubes 48 and 49 to develop a balancedsinusoidal output voltage for vertical deflection across load resistors50 and 5| provided for tubes 48 and 43, respectively. This v outputvoltage is applied to the vertical deflecting plates 23, 24 throughcoupling condensers 52, 53. A resistor 54 is coupled between verticaldeflecting plate 23 and a tap on potentiometer 41 to provide verticalcentering of the cathode-ra beam of tube l5 prior to deflection. Inorder to provide for.scanning of the patterns of target electrode IS ina path, as represented by the dottedline path A, B, C, D of Fig. 2, thatis, in substantially circumferential paths having angular portionsradially displaced on target electrode l9 and corresponding to thedissimilarity of the successive field periods of the desiredsynchronizing signal, there is provided I ic intervals during theframe-scanning cycle of the system. This means comprises means forperiodically varying the amplitudes of the scanning fields of thecathode ray tube l5. For this purpose, a keying signal is developed by aunit 55 which is utilized alternately to increase and decrease theamplification of tubes 39, Q and 45, 49. The unit 55 comprises tubes 56and 51, to the input electrodes of which are applied, respectively, thevoltage across condenser 3| and the voltage across resistor 32. Thesevoltages are in quadrature and, therefore, a 60-cycle voltage having aphase determined by the relative amplification of tubes 55 and 51 isdeveloped across a load resistor 58 whichis common to tubes 56 and 51.Variable degenerative cathode resistors 59 and 50 are provided,respectively, for tubes 56 and 51 in order that the relativeamplification of will be seen that the amplitude of the quadraturespace-displaced and phase-displaced scanning fields of cathode-ray tubeI5 is periodically varied at aBO-cycle'rate, thus causing thecathode-ray beam to travel in circular paths of different diameters onthe surface of target electrode l9. Furthermore, it will be seen thatresistors 59 and 50 provide a suitable means for manually ad'- justingthe phase of the 30-cycle keyingsignal and that the system may beadjusted so that the radial change in the scanning of the patterns ontarget electrode I9 takes place during the scanning of thefield-synchronizing patterns F, F.

Therefore, the system described is effective to develop a suitablecomposite synchronizing signal across load resistor 25 for a doubleinterlaced scanning cycle of 18% lines per field and 3'? lines perframe, 4 bread field-synchronizing pulses being developed during eachfield-retrace interval the tubes can be adjusted, thereby to develop anoutput voltage across load resistor 58 of any desired phase relationshipwith respect to the supply voltage to transformer 28.

The signal output of tubes 55 and 51 is utilized to synchronize aconventional multivibrator relaxation oscillator, having a frequencyequal to half that of the supply voltage of the system. that is, 30cycles per second, and comprising vacuum tubes BI and 62 and a loadresistor 53. The circuit constants of the relaxation oscillator are soproportioned that the signal output derived from resistor 63, comprisingsynchronous keying pulses, is of rectangular wave form with positive andnegative pulses of equal duration, as indicated by the curve W shownadjacent theretof The keying signal so derived is applied with asuitable amplitude,- which is adjustable by means of a tap on resistor63, to the screen grids of tubes 39, 40 and 48, 49 to alter the ain ofthese tubes.

In considering the operation of the system just described, it will beseen that as the cathode ray beam of tube I5 is incident on variousportions of the pattern of the target electrode l9, synchronizing-signalcomponents are developed across a of the system. It will be understoodthat a suitable output voltage could also be taken from a load circuitcoupled to collector electrode 20 rather than from target electrode I9,as described.

In Figs-3a and 3b of thedrawings, there are illustrated in detailportions of a composite synchronizing signal for successive fieldsconforming to the present standards of the Radio ManufacturersAssociation." This signal comprises linedoubling or equalizing pulses Dand field synchronizing pulses F for each field period,line-synchronizing pulses L for one field period, and line pulses L forthe succeeding field period which are displaced one-half of the lineperiod fromthe line varies as the scanning beam is, or is not,incidenton one of the target patterns of target electrode l9. Furthermore, itwill be seen that, if the scanning of target electrode I9 is in a pathsuch as is indicated by A, B, C, D in Fig. 2, a composite synchronizingsignal is developed for the transmitting circuit III of 18line-synchronizing pulses per field period, 37 line-synchronizing pulsesper frame period, and 4 broad pulses during each field-retrace period,the generated synchronizing signal thus being suitable for doubleinterlace scanning systems. Furthermore, it will be seen that neglectingthe efi'ect of unit 55, the

- quadrature space-displaced and time-displaced scanning fieldsdeveloped by the deflecting plates of cathode-ray tube l5 due to thevoltages applied thereto from tubes 35, 40 and .48, 49 would cause thecathode-ray beam of tube l5 to be driven in a circle at the frequency ofthe power supply source utilized to energize the primary winding oftransformer 28. In considering theoperation 'of the complete'system justdescribed.

in view of the partial descriptions given above, it

pulses L of the first field period. A portion of a target electrode l9corresponding .to target electrode I9 of Fig. 1 is shown in Fig. 30having patterns thereon suitable for developing a compositesynchronizing signal conforming to the above-mentioned standards;portions of the pattern of element I9 which correspond to patternportions of element l9 have similar reference numerals.

It is believed that the operation of the modification of the inventionillustrated inFigsalia, 3b

and 30 will be readily understood from the de-- scription given withreference to the operation of Fig. 1, and it will be understood that thepatterns of element 19' are scanned in a path A, B, C, D, correspondingto path A, B, C, D of Fig. 2.

In Fig. 4 there is illustrated schematically a televisionsynchronizing-signal generator-in accordance with the inventionutilizing a scanning disc in place of the synchronously-operatedcathode-ray tube 15 of Fig. 1. The generator of Fig. 4 thus comprises ascanning disc I0 operated by a motor H through suitable supply leads 12,13. The motor H is of the synchronous type and scanning disc 10comprises thereon a series Jiil - the inner circumferential patternpath. A suit I of slots arranged in a pattern corresponding to either ofthe target patterns described above. In order to develop a suitablesynchronizing signal from the arrangement, a light source is providedincluding lamps H and 15. lamp 14 being dis-v posed to transmit lightthrough the apertures in the outer circumferential pattern path and'lamp 15 being disposed to transmit light through able synchronous switchI5 is'provided for energizing lights 14 and I5 alternately while aphoto-sensitive device 1|, responsive to light transmitted through theapertures in disc Ill,

is utilized to develop a composite synchronizing signal which isthereafter supplied to an ampli fler 18, from the output terminals I9and of which is derived the desired composite syn-. chronizing signal.The synchronous switch 18 may be similar to the synchronous keying unit55 of Fig. 1 and is so arranged that one of the lights 14, is alwaysenergized and the switching is That is, it is immaterial above-mentionedstandards, a pattern including 441 radial bars is required, the barscorresponding to the line-synchronizing pulses during a completeframe-scanning cycle.

These bars must be resolved in thescanning process, which requires acathode-ray beam having an extremely fine .spot size at the target or atarget electrode in the cathode-ray tube of a very large diameter. Themodification of the invention illustrated in Fig. 5 is one in whichthese severe requisites are not present. In the arrangement of Fig. 5,the cathode-ray beam is caused to traverse the same circular path aplurality of times during each field period in order to generateline-synchronizing components and is then radially-displaced to scananother pattern to generate field-synchronizing components andline-doubling components so that a composite synchronizing signal inaccordance with the R. M. A. standards is developed. In order to effectrotation of the cathode-ray beam at the relatively high frequencyrequired, an oscillator 95 is providedfor generating sinusoidaloscillations at a frequency of 630 cycles per second,

. the oscillator being synchronized from the power source 88,representing the alternating current source supplying the transmitterfor which the synchronizing signal is to be generated. Phasedisplacedvoltages are supplied from oscillator 85 to the cathode-ray tube of thesystem, through a phase adjuster 81 and suitable phase-splittingcircuits and amplifiers similar to those of Fig. L Circuit elements inFig. 5 which are similar to those of Fig. 1 have identical referencenumerals with the addition of a prime. Thus, the circuit '01 Fig. 5comprises a phase-splitting circuit including a series-connectedresistor 88 and condenser 89 coupled across a winding 98 which,

in turn, is coupled to the output circuit of phase adjuster 81, forsupplying a voltage of suitable tube 98. In order to develop a balancedoutput voltage, there is provided a-phase-inverting tube III, thecontrol grid of which is connected by means of tap 95 to load resistorII of tube Hill. A common cathode resistor 96 is provided for tubes I88and III. In order to scan angular portions or the target electrode incircumferential paths which are radially-displaced. there is provided apulse generator 91, the function of tube I 00 in quadrature with thatapplied to a which is analogous to that of generator 55 of Fig. 1 andwhich may be of a similar type. The pulse generator 91 is synchronizedby the alternating current source and is adapted to provide arectangular-pulse wave form, the period I of the pulses being 60 cyclesper second. The output of pulse generator 91 is of rectangular;

wave 'form with the duration of the positive pulses that of the negativepulses, as illustrated by curve W adjacent thereto. This pulse output ofgenerator 91 is applied to the screen electrodes of tubes 98, 99, I00,and I iii in order to increase the amplification of these tubes duringthe positive pulses and decrease such amplification during the negativepulses.

In utilizing the modification of the invention illustrated by thecircuit of Fig. 5, the cathoderay tube is provided with a targetelectrode in accordance with that represented by target electrode IQ" ofFig. 6. This target electrode comprises a pattern in which substantiallyall of the outer circumferential path corresponds to field 1synchronizing components and line-doubling components of the signalwhich is to be generated, that is, to the field-retrace interval, whilesubstantially all of the inner circumferential paththereof correspondsto line-synchronizing components to be generated. The signal to begenerated can thus be considered to consist of line-synchronizingcomponents, line-doubling components, and field-synchronizing componentscorresponding to one field period, and line-doubling andfield-synchronizing components for a succeeding field period which aredifferently spaced with reference to the line-synchronizing componentsthan those of the first-mentioned field period.

In considering the operation of the system of Fig. 5, it will be seenthat quadrature phasedisplaced sinusoidal voltages of 630 cycles areapplied to the deflecting plates of the cathoderay tube and that, in theabsence of any further control, the cathode ray of the tube would berotated in a circular path at a frequency of 630 cycles. However, asexplained in connection with the circuit of Fig. 1, the amplitudes ofthe deflecting voltages supplied to the cathode-ray tube i5 arealternately increased and decreased by means of the applied pulsevoltage.

The deflection potentials of the cathode-ray tube 15 of the modificationof the invention illustrated in Fig. 5 are adjusted so that thecathoderay beam of the tube scans a circular pattern corresponding tothe inner'path illustrated on the target electrode IQ" of Fig. 6 duringthe negative pul'sesfrom generator '91, and, during a positive pulsefrom generator 91, the cathoderay beam scans the outer circumferentialpath. The relative phase of the scanning potentials supplied to thedeflecting plates and the pulses from generator 91 is adjusted by meansof phase adjuster 81 so that the amplitude of the scanning potentials iscaused to increase just before components corresponding to line-doublingand field-synchronizing components are to be generated and to decreasejust after such components have been generated, Therefore, it will beseen that the cathode-ray beam of tube 15 is caused to scan the patternillustrated by the dotted lines of Fig. 6. That is, beginning at pointA", a pattern is scanned corresponding to one set of field-synchronizingand line-doubling components while, at point B", the scanning beam isswitched back to the inner circle to scan portions oi the patterncorresponding to imam time the inner pattern is again scanned aplurality of times in order to generate line-synchronizing componentsfor the succeeding field period,

after which the cycle repeats.

It will be noted that there are 21 line bars on the inner circle oftarget electrode l9" which also extend to the outer circle so that in 10revolutions of the scanning beam on the inner circle and one-halfrevolution on the outer circle, a field of 220.5 lines is scanned,corresponding to. a total of 441 lines for the complete frame cycle of21 revolutions.

It will also be understood that the principle the invention illustratedin Fig. is not limited to the particular scanning frequencies and theparticular pattern shown but that the modification of the inventionillustrated in Fig. 5 may be utilized with other scanning patterns anddifferent numbers of bars on the target pattern. Furthermore, it will beunderstood that the principle of the invention illustrated in Fig. 5 isequally applicable to a system using other types of interlaced scanning.For example, in a systern utilizing triple'interlace'd scanning, thetarget electrode can be provided. with three groups of patterns on theouter circle representing the field-synchronizing pulses together withtheir associated line-doubling pulses for each of the three successivefield-retrace intervals, and each of these patterns would then cover anangular portion of 120 degrees of the outer circumferential path.

While there have been described what are at present considered to be thepreferred embodiments of the invention, it will be apparent to thoseskilled in the art that various changes and modifications may be madetherein without departing from the invention, and it is, therefore,aimed in the appended claims to cover all such changes and modificationsas fall within the true spirit and scope of the invention.

What is claimed is: a

1. A synchronizing-signal generator for a television transmitter adaptedtogenerate a syn-' chronizing signal for use in a multiple-interlacescanning system-in which synchronizingcomponents thereof during onefield period are different from those during a succeeding field periodcomprising, a device having a plurality of radiallydisplacedcircumferential patterns having Predetermined'angular portions thereofcorresponding to predetermined portions of the signal to be generated,and means for continuously scanning said patterns in successivesubstantially circumferential paths having predetermined angularportions radially displaced on said device and corresponding to thedisslmflarity of said field periods of the desired synchronizing signalto develop an electrical signal corresponding to the patterns scanned.

2. A synchronizing-signal generator for a television transmitter adaptedto generate a synchronizing signal for use in a multiple-interlacescanning system in which synchronizing components thereof during onefield period are different components and field-synchronizing componentspaths having predetermined angular portions radially displaced on saiddevice and corresponding to the vdissimilarity of said field Periods ofthe desired synchronizing signal to develop an electrical signalcorresponding to the patterns scanned.

3..A synchronizing-signal generator for a television transmittei'adapted to generate a synchronizing signal including line-synchronizingfor use in. a multiple-intei'lace scanning system in which synchronizingsignals during one field period are different from those during asucceedmg field period comprising, a device having a plurality ofradially-displaced circumferential patterns having predetermined angularportions thereof corresponding, respectively, to the porhum of me signalto be generated including the line-synchroniz ng components, saidpatterns corresponding to the line-syncnronlzlng components or one neldperiod being dliierently spaced Wit-1'1 reierence to tnose correspondingto the field-sylicni'onlzing components than those corresponding tomellne-syncnrunlznig components or a succeeding nerd period, and meansior contmuously scanning said patterns in successive substantiallycircumierentlal paths having predetermined angular portions radially dislaced components and field-synchronizing components r for use in agnultlple-interlace scanning system in which synchronizing componentsduring one Iield period are dinerent iro'm those during a succeedingnerd period comprising, a device having a plurality orradially-displaced clrcnnlierentlal patterns navmg dlnerentpredetermined portions thereof corresponding to toe field-syncnronlzlngcomponents to be generated and to the line-synchronizing components tobe gen-- erased, and means ior contmuously scanmng said patterns insuccessive 'suoscantially cllcumlerenmal paths having predeterminedangular portions radially displaced on said device and corresponding tothe dissimilarity or said field periods of trie desired sync ronizingsignal to develop an electrical signal corresponding to the patternsscanned.

5. A synchronizing-signal generator for atelevision transmitter adaptedto generate a synchronizing signal including line-synchronizmgcomponents, equalizing components, and fieldsynchronizing components foruse in a multipleinterlace scanning system in which synchronizingcomponent during one field period are different from those during asucceeding field period com-- prising, a device having a plurality ofradiallydisplaced circumferential patterns having predetermined portionsthereof, respectively, corre-' spon'ding to the field-synchronizingcomponents and equalizing components to be generated and to theline-synchronizing components to be generated, and means forcontinuously scanning said patterns in successive substantiallycircumferential paths having predetermined angular portions radiallydisplaced on said device and corresponding to the dissimilarity of saidfield periods of the desired synchronizing signal to develop anelectrical signal corresponding to the patterns scanned.

6. A synchronizing-signal generator for a television transmitter adaptedto generate a synchronizing signal including line-synchronizingcomponents and field-synchronizing components for use in amultiple-interlace scanning system in which synchronizing componentsduring one field period are different from those during a succeedingfield period comprising, a device having a plurality ofradially-displaced circumferential pattern including substantially anentire circumferential path corresponding to thefieldsynchronizingcomponents to be generated and the remaining patternscorresponding to the line-synchronizing components to be generated,

and means for continuously scanning said patterns in successivesubstantially circumferential paths having predetermined angularportions radially displaced on said device and corresponding to thedissimilarity of said field periods including means for scanning saidpattern portions corresponding to the line-synchronizing components aplurality of times for each scansion of said pattern portioncorresponding to the fieldsynchronizingcomponents to develop anelectrical signal corresponding to the pattern scanned.

'7. A synchronizing-signal generator for a television transmitteradapted to generate a synchronizing signal including line-synchronizingcomponents and field-synchronizing components for use in amultiple-interlace scanning system in which synchronizing componentsduring one field period are different from those during a succeedingfield period comprising, a device having a plurality ofradially-displaced circumferential patterns having predeterminedportions thereof, respectively, corresponding to the fieldsynchronizingcomponents to be generated and to the line-synchronizing components tobe generated, and means for continuously scanning said patterns insuccessive substantially circumferential paths having predeterminedangular portions radially displaced on said device and correspond ing tothe dissimilarity of said field periods including means for scanningsaid pattern portions corresponding to the line-synchronizing componentsa plurality of times for each scansion of said pattern portioncorresponding to the fieldsynchronizing components to develop anelectrical signal corresponding to the pattern scanned.

8. A synchronizing-signal generator for a television transmitter adaptedto generate a synchronizing signal including line-synchronizing "periodsof the desired synchronizing signaland including means for scanning saidother portion a plurality of times for each scansion of said one portionto develop an electrical signal correspending to the pattern scanned.

9. A synchronizing-signal generator for a television transmitter adaptedto generate a synchronizing signal for use in a multiple-interlacescanning system in which synchronizing components during one fieldperiod are difierent from those during a succeeding field periodcomprising, a cathode-ray tube including a target having thereon aplurality of radially-displaced circumferential patterns havingpredetermined angular portions thereof corresponding to predeterminedportions of the signal to be generated, means for continuously scanningsaid target in successive substantially circumferential paths havingpre-' determined angular portions radially displaced on said device andcorresponding to the dissimilarity of said field periods of thedesiredsynchronizing signal to develop an electrical signalcorresponding to the patterns scanned.

10. A synchronizing-signal generator for a television transmitteradapted to generate a synchronizing signal for use in amultiple-interlace scanning system in which synchronizing componentsduring one field period are different from for periodicallyvvarying theamplitude of said fields for continuously scanning said target insuccessive substantially circumferential paths having predeterminedportions radially displaced on said target and corresponding to thedissimilarity of said field periods to develop an electrical signalcorresponding to the patterns scanned.

11. A sychronizing-signal generator for a television transmitter adaptedto generate a synchronizing signal for use in' a multiple-interlacescanning system in which synchronizing components during one fieldperiod are different from those during a succeeding field periodcomprising, a cathode-ray tub'e including a target having thereon aplurality of radially-displaced circumferential patterns havingpredetermined angular portions thereof corresponding to predeterminedportions of the signal to be generated, means for generating quadraturespace-displaced and time-displaced sinusoidal scanning fields to scansaid target in a circular path, means for generating synchronous keyingpulses, and means for utilizing said keying pulses periodically to varythe amplitude of said scanning fields continuously to scan said targetin successive sub stantially circumferential portions havingpredetermined paths radially displaced on said target and correspondingto the dissimilarity of said field periods to develop an electricalsignal corresponding to the pattern scanned.

12. A synchronizing-signal generator for a mined angular portionsthereof corresponding to predetermined portions or the signal to begenerated, means including a photosensitive device and a light-sourcemeans for continuously scanning said apertures in successivesubstantially circumferential paths having predetermined angularportions radially displaced on said device and corresponding to thedissimilarity of said field periods of the desired synchronizing signalto develop an electrical signal corresponding to the apertures scanned.

13. A sychroni'zing-signal generator for a television transmitteradapted .to generate a synchronizing signal for use in amultiple-interlace scanning system in which synchronizing componentsthereof during one field period are different from those duringa'succeeding field period comprising, a scanning disc having thereinapertures forming a plurality of radially-dis- 4 placed circumferentialpatterns having predetermined angular portions thereof correspondingtopredetermined portions. of the signal to be generated, means includinga photosensitive device and a light-source means for continuouslyscanning said apertures in successive substantially circumferentialpaths, means for generating synchronous keying pulses, and means forutilizing said keying pulses to shift the scanningpath so-that saidapertures are scanned in substantially circumferential paths havingpredetering to the apertures scanned.

mined angular portions radially displaced on said- HAROLD M. LEWIS.

